This invention relates to hemorheological measurement and, more particularly, to a blood filter, a method of and apparatus for hemorheological measurement
Conventionally, membranes which have very small holes, e g., "Nuclepore" filters and nickel mesh filters are used to examine the filterability when blood passes through the filter, as described on pages 42 to 43 of the collection of papers prepared for the meeting of Nippon Biorheology Gakkai in 1988 (No. 7-31, 7-33 and 7-34). A "Nuclepore" filter is formed of a thin polycarbonate sheet with small holes formed therein, and a nickel mesh is formed of a thin nickel film with small holes formed therein. These types of filters are used in such a manner that blood is made to pass through the small holes by applying different pressures on the two sides of the filter membrane respectively, and that the time taken for the blood to pass through the filter is measured to estimate the filterability or the deformability of red blood cells.
Also, a method of using a filter constructed by forming small holes in an Si.sub.3 N.sub.4 membrane formed on a surface of a silicon substrate to evaluate the deformability of red blood cells is known. An example of this method is described on pages 2,191 to 2,196 of the Denshi Jyoho Tsushin Gakkai Lecture Magazine D (1988).
In these conventional techniques, the sectional configuration of blood cells in the direction of passage through the filter cannot be observed although the existence of blood cells can be observed at the outlet or inlet of the filter.
Other problems are also encountered in that the length of the flow passages of the filter cannot be freely selected, that information on the size or volume of one blood cell cannot be separately obtained, and that blood cells passing through the holes of the filter are not uniformly deformed.